Mesoplatys ochroptera Stål, Exosoma and Ootheca spp. seriously damage sesbania, Sesbania sesban (L.) Merril, a multipurpose leguminous tree widely used in tropical agroforestry. This is discouraging farmers from expanding the planting of sesbania in various agroforestry systems in eastern and south-central Africa. Rapid methods are needed for estimation of population densities of these beetles for decisionmaking in pest management. A study was conducted with the objectives of determining the existence of any positive relationship between the occupancy and abundance of Mesoplatys, Exosoma and Ootheca and determining the model that best predicts abundance from occupancy for rapid estimation of population densities. The Poisson model assuming spatial randomness, the negative binomial distribution (NBD) model assuming spatial aggregation, the Nachman model without any distribution assumption, and a General model incorporating spatial variance-abundance and occupancy-abundance relationships were fitted to data on adult M. ochroptera, Exosoma and Ootheca from western Kenya, southern Malawi and eastern Zambia. Very strong variance to abundance relationships were observed in the spatial pattern of all three beetles. The occupancy-abundance relationships were also positive and strong in all beetles. The occupancy and abundance predicted by the four models were closest to the observed at lower densities compared with higher beetle densities. At higher population densities, the NBD and the General model gave better fit for M. ochroptera and Exosoma. For Ootheca populations, the Poisson and NBD models gave better fit at higher population densities. The relationships established here can be used as guide to estimate beetle densities for decision-making in pest management.

Physcus seminotus Silv. (properly P. sp. nr. seminotus Silv.) and P. subflavus Annecke & Insley (Aphelinidae) are parasites of the sugar-cane scale insect Aulacaspis tegalensis (Zhnt.) (Diaspididae) in East Africa and they have been purposely introduced into Mauritius where A. tegalensis is an important pest. P. seminotus has brachypterous, flightless females and P. subflavus winged females but their biology is essentially similar. The parasites are arrhenotokous and fertilised and unfertilised eggs are deposited in different sites concomitant with development of female and male larvae on different primary hosts. Female larvae develop endoparasitically in A. tegalensis from fertilised eggs deposited in the host's body cavity. Male larvae develop ectoparasitically on immature Hymenoptera in A. tegalensis from unfertilised eggs deposited in the air-filled cavity of the latter's integumentary remnant. The males of the two Physcus spp. are therefore hyperparasitic and they frequently develop on the immature stages, both male and female, of their own kind (autoparasitism). Unfertilised eggs are laid by virgin females and also by mated females, the latter being able to deposit fertilised and unfertilised eggs at will, depending on the egg site encountered. Sexual dimorphism occurs at all stages, including the deposited egg. The preovipositional adult is the preferred stage of A. tegalensis for deposition of fertilised eggs and development of females is most rapid in such hosts. Development in young hosts is arrested until the hosts have grown to virtually their full size. The host of a male is apparently a matter of chance in so far as evelopment will occur on larval and pupal Hymenoptera of various species found in the empty, inflated, brittle integument of parasitised A. tegalensis. Only one individual, whether male or female, develops per host. Oviposition behaviour of mated females is such that superparasitism is largely avoided but it is liable to occur frequently when virgin females oviposit. Adult females will feed on the body fluids of A. tegalensis that are released by insertion of the ovipositor and also on sugary fluids. They live a month or more, ovipositing continually at a gradually decreasing rate, and laying usually 50–100 eggs.

The susceptibility of larvae of the diamondback moth, Plutella xylostella Linnaeus to purified crystal proteins and spore–crystal preparations of Bacillus thuringiensis was investigated for 13 populations from seven states in India. The LC50 (μg ml−1, 48 h) values of Cry proteins for different populations of P. xylostella ranged from 0.14–3.74 (Cry1Aa), 0.007–1.25 (Cry1Ab), 0.18–2.47 (Cry1Ac) and 0.12 – 3.0 (Cry1C). The LC50 (mg (ai) l-1, 48 h) of spore-crystal preparations ranged from 0.02–0.98 (HD-1) and 0.06–2.14 (HD-73). Significantly higher LC50 values for all tested toxins and strains were obtained with populations collected from Iruttupallam and Ottanchathiram in the southern state of Tamil Nadu, whereas some of the populations collected from the northern part of India were more susceptible than the susceptible IARI 17–65 population. The high levels of resistance in the Iruttupallam and Ottanchathiram populations to Cry1Ab suggested selection pressure by Cry1Ab, which is the predominant toxin in B. thuringiensis formulations used in India. Cry1Ab was found to be more toxic than the other toxins. The population from Iruttupallam showed increased resistance following selection with Cry1Ab in the laboratory (LC50 from 1.25 to 4.31 μg ml−1 over two generations) and also showed cross resistance to Cry1Aa and Cry1Ac. The resistance to Biobit® in the field population from Iruttupallam declined slowly; requiring c. 33 generations for an overall 10-fold decline in LC50 when the insects were reared in the laboratory without exposure to B. thuringensis.

The developmental, survivorship and reproductive biology of Eretmocerus sp. nr furuhashii Rose & Zolnerowich parasitizing Bemisia tabaci (Gennadius) biotype B on tomato, cucumber, eggplant and collard at 26±0.5°C was studied. The mean longevity ranged from 6.5 days on tomato to 8.1 days on collard. The mean lifetime fecundities on tomato, cucumber, eggplant and collard were 35.4, 37.3, 41.4 and 46.4 eggs, whereas the mean lifetime fertility was 20.2, 22.7, 28.3 and 33.6 offspring, respectively. Developmental time was longest on cucumber (17.1 days) and shortest on collard (15.9 days). Survival rates varied significantly across host plants. Sex ratio (♀:♂) varied from 1.71 to 1.93 across the four hosts. The intrinsic rate of increase (rm) was highest (0.157) on collard and lowest on tomato (0.133). Mean generation time (R0) ranged from 14.7 to 20.9 days. All the data demonstrated that the reproductive success and overall performance of E. sp. nr furuhashii increased as the density of leaf hairs declined. As leaf hairs play a key role in determining efficacy, it is unlikely that effective biological control of B. tabaci using E. sp. nr furuhashii will be achieved on non-glabrous crop varieties.

Predators are important determinants of the spatiotemporal distribution of prey within a given habitat. The predator effects may vary with diet specialisation, the associated risk posed to prey and, if multiple predators are present, the predator-predator interactions. We examined the spatiotemporal distribution of the herbivorous spider mite Tetranychus urticae and the associated specialist and generalist predators Phytoseiulus persimilis and Neoseiulus californicus on bean plants. Tetranychus urticae is a key pest on numerous agricultural crops. Both predators are used singly and in combination for biological control of spider mites. Population development and within-plant distribution of the spider mites and the predators were compared among five treatments: T. urticae without predators, with either predator alone and with both predators in combination at full and half densities. The spider mites were suppressed to zero density in both predator combination treatments but not in the single predator treatments. The predators determined the spatiotemporal distribution of the spider mites through density- and behaviour-mediated effects, and these effects were linked to diet specialisation. The specialist P. persimilis exerted stronger density-mediated effects on the spider mite distribution than did the generalist N. californicus. Either predator induced in the spider mites early upward migration on plants. The predators also affected each other's distribution. The aggregation level of N. californicus was lowered by P. persimilis but not vice versa. In combination, the predators were more dispersed than when alone, reducing the predator-free space and leading to the local extinction of T. urticae.

Laboratory and field studies were made to study the flight behaviour and development of thoracic musculature in male Glossina morsitans orientalis Vanderplank collected as adults near Kariba, Rhodesia, or emerged from puparia collected there. Muscular development, measured as thoracic residual dry weight, was significantly inhibited by confinement in the laboratory and flight activity declined when laboratory-emerged flies were maintained in the laboratory. Survival of laboratory-emerged flies in the field was only 17% that of field-emerged flies. Irreversible behavioural and physiological inhibition in flight and in flight musculature is therefore believed to occur within the first few hours of adult life as a result of confinement; 70–80% of the confined population was affected. These inhibitions can be avoided by using field-emerged adults for field trials.

1. Fly rounds and reconnaissances about Sambala have indicated the following types of fly community: (a) Compact “female centres” characterised by frequent passage of game, and showing high apparent female percentage and often apparent concentration of fly; (b) “spread centres” over larger areas believed to be comparable in function to true, compact “female centres”; (c) “male areas” spread over large areas of Berlinia-Brachystegia and sometimes other kinds of wooding, where the apparent female percentage is low; (d) areas where fly is scarce.

2. Investigation of these phenomena by field experiments and other methods has led to the conclusion that the “female centres” and “spread centres” are most probably feeding-grounds of fly, and that the “male areas” are its home.

3. It is difficult to draw reliable conclusions from fly-rounds on the apparent variations of fly numbers in time, in relation either to season or to movements of game.

1. The conditions of temperature and humidity under which Xenopsylla cheopis is able to complete its metamorphosis are described.

2. The larvae and pre-pupae are easily killed by drying, but the pupae are not. The cocoon does not protect the larva from drying.

3. Development is much quicker at high than at low temperatures.

4. The rate of loss of water from the larva appears to be proportional to the saturation deficiency of the air, at any rate at 18°C., 22°C. and 29°C.—when the time which elapses between spinning the cocoon and the formation of the pupa is taken into account.

The writer is indebted to Dr. P. A. Buxton for reading and criticising the manuscript.

Age structures and reproductive anomalies of two field populations of Glossina pallidipes Austen in Zimbabwe were compared. One population was treated with insecticide sprayed on odour-baited targets, while the other was left undisturbed. Both populations were sampled with F3 prism-type traps. Capture probabilities were higher for females in early stages of pregnancy than for those in later stages. Per-capita mortality rates were estimated from age distributions which had been corrected for rate of increase. The mortality rate steadily increased over time in the insecticide-treated area but remained roughly constant in the undisturbed area. Estimates of mortality had wide confidence intervals, and the mortality model is critically reviewed. No evidence was seen in the treated population for an increased incidence of abortion or other reproductive anomalies, or for a decrease in insemination rate.

Groups of gravid females of Lucilia cuprina (Wiedemann) in a 1-m3 cage flew upwind in response to sheep placed upwind of the cage. No downwind flight or other response was observed to sheep placed downwind of the fly cage. Flystruck sheep stimulated the greatest accumulation of flies on the upwind cage wall (46% of the caged flies), followed by sound wet sheep (29%) and sound dry sheep (19%). All sheep tested caused significantly more flies to accumulate on the upwind wall than did controls consisting of either no bait or a man placed upwind (14%). Struck sheep elicited significant upwind movement of flies at distances of up to 20 m; sound, dry sheep did so only up to 10 m. It was concluded that L. cuprina is able to orient from a distance in response to volatile sheep kairomones; kairomones from dry sheep are augmented by wetting or the presence of cutaneous myiasis, as indicated by an enhanced fly response. The experiments performed did not exclude a role for visual or thermal cues in blowfly orientation to sheep.

The neurosecretory cells of the pars intercerebralis, the corpus cardiacum and the corpus allatum were examined in histological sections of Glossina austeni Newst. females fixed at daily intervals over the first two cycles of pregnancy. Two groups of neurosecretory cells corresponding to the lateral and median cells of other insects were recognised. The median neurosecretory cells were found to undergo cyclic changes of net synthesis and net release, which were correlated with ovulation and larviposition. The single ellipsoid corpus allatum undergoes cyclic changes in volume and histological appearance which are correlated with changes in the volume of the milk gland.

The brown planthopper Nilaparvata lugens Stål is one of the major insect pests of rice Oryza sativa L. The host resistance exhibits profound effects on growth, development and propagation of N. lugens. To investigate the molecular response of N. lugens to host resistance, a cDNA-amplified fragment length polymorphism (cDNA-AFLP) technique was employed to identify the differentially expressed genes in the nymphs feeding on three rice varieties. Of the 2800 cDNA bands analysed, 54 were up-regulated and seven down-regulated qualitatively in N. lugens when the ingestion sources were changed from susceptible rice plants to resistant ones. Sequence analysis of the differential transcript-derived fragments showed that the genes involved in signalling, stress response, gene expression regulation, detoxification and metabolism were regulated by host resistance. Four of the transcript-derived fragments corresponding to genes encoding for a putative B subunit of phosphatase PP2A, a nemo kinase, a cytochrome P450 monooxygenase and a prolyl endopeptidase were further characterized in detail. Northern blot analysis confirmed that the expression of the four genes was enhanced in N. lugens feeding on resistant rice plants. The roles of these genes in the defensive response of N. lugens to host plant resistance were discussed.

A cytotaxonomic study was carried out on 13 species of Encarsia Förster, known to parasitize aleyrodids and diaspidids. The chromosomes varied greatly both in number and morphology, with E. protransvena Viggiani having the lowest chromosome number (2n = 6) and E. asterobemisiae Viggiani & Mazzone the highest (2n = 20). The most common chromosome number was 2n = 10. C-banding, G-banding and silver staining for nucleolar organizer regions (NOR) provided the possibility of distinguishing between karyotypes with the same chromosome number and morphology and to identify all the pairs of homologues in a diploid set for advanced cytogenetic studies. The karyotype of Coccophagus lycimnia (Walker) was also examined. The chromosome data suggested that in Encarsia, karyotype differentiation has mainly occurred through a series of centric fusions, although other rearrangements may also have been significant. The importance of karyological data in systematic studies and in the identification of biotypes and cryptic species of economic interest is outlined.

Two stable infections of Wolbachia pipientis, wMelPop and wMel, now established in Aedes aegypti, are being used in a biocontrol program to suppress the transmission of dengue. Any effects of Wolbachia infection on insecticide resistance of mosquitoes may undermine the success of this program. Bioassays of Ae. aegypti were conducted to test for differences in response to insecticides between Wolbachia infected (wMelPop, wMel) and uninfected lines. Insecticides screened were bifenthrin, the pyrethroid commonly used for adult knockdown, as well as larvicides: Bacillus thuringiensis var. israelensis, the organophosphate, temephos and the insect growth regulator, s-methoprene. While differences in response between lines were detected for some insecticides, no obvious or consistent effects related to presence of Wolbachia infection were observed. Spreading Wolbachia infections are, therefore, unlikely to affect the efficacy of traditional chemical control of mosquito outbreaks.

Field experiments carried out in 1945 at Rosh Pina in Palestine have proved the great efficiency of DDT residual spray in houses against sandflies.

A high degree of protection against P. papatasii, P. major and P. chinensis was obtained by inside spraying of rooms with DDT in kerosene.

The residual action lasted for 52–58 days during the hot summer months. At the end of this period the effect was still undiminished but the end of the sandfly season made further observations impossible. Judging from observations made elsewhere it may be assumed that the residual effect would have lasted not more than another two weeks.

Dosage of 1 g. per m2 (100 mg. DDT per sq. ft.) was fully effective, and 2 g. per m2 gave no better results. The best method of application is the treatment of all internal surfaces (walls and ceiling). As sandflies tend to congregate in the angle between wall and ceiling, treatment of walls and this angle only gives equally good results.

An attempt to protect a house by spraying “barriers” (vertical surfaces of stone walls etc., within a radius of 50 metres) failed. Sandflies on the outside surfaces disappeared after the DDT treatment but the observations recorded here and those reported by other authors suggest that much larger areas would have to be sprayed in order to make this method effective.

A marked reduction of sandflies in untreated rooms followed the spraying of other Tooms in the same house with DDT. The mechanism of this phenomenon is explained. A general reduction of the sandfly population can be expected when large-scale DDT treatment is carried out in a village or camp area.

Ribonucleic acid interference (RNAi) is a sequence-specific gene silencing mechanism induced by double-stranded RNA (dsRNA). Recently, RNAi has gained popularity as a reverse genetics tool owing to its tremendous potential in insect pest management, which includes Helicoverpa armigera. However, its efficiency is mainly governed by dsRNA concentration, frequency of application, target gene, etc. Therefore, to obtain a robust RNAi response in H. armigera, we evaluated various concentrations of dsRNA and its frequency of applications delivered through diet in silencing a midgut gene, chymotrypsin and a non-midgut gene, juvenile hormone acid methyl transferase (jhamt) of H. armigera. The extent of target gene silencing was determined by employing reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR). Our study revealed four significant findings: (i) single application of dsRNA elicited a delayed and transient silencing, while multiple applications resulted in early and persistent silencing of the above genes; (ii) silencing of the non-midgut gene (jhamt) through diet delivered dsRNA revealed prevalence of systemic silencing probably due to communication of silencing signals in this pest; (iii) the extent of silencing of chymotrypsin was positively correlated with dsRNA concentration and was negatively correlated with jhamt; (iv) interestingly, over-expression (15–18 folds) of an upstream gene, farnesyl diphosphate synthase (fpps), in juvenile hormone (JH) biosynthetic pathway at higher concentrations of jhamt dsRNA was the plausible reason for lesser silencing of jhamt. This study provides an insight into RNAi response of target genes, which is essential for RNAi design and implementation as a pest management strategy.

The status of the Mediterranean fruit fly in Israel is reviewed briefly. Apricots, peaches and guavas are the most severely attacked of the summer fruits.

The ecology of the various stages of the insect is discussed. It is pointed out that, in addition -to temperature, the type of food influences the length of development of the larva. The threshold of development in the temperature development hyperbola has been calculated and found to be between 10–11°C.

The threshold of development of the pupae was found to be close to 11CC. A daily exposure of the pupae for six hours at a temperature of 32–37°C. caused no injury, but a similar exposure at 42°C. brought about a heavy mortality. At 46°C. one hour's exposure resulted in considerable injury whilst three hours' exposure killed 80 per cent, of the pupae. This explains the very high mortality of the pupae in the groves during June, July and August.

A study of the development of the eggs in the ovarioles at various degrees of temperature indicated that at 18–22°C. no appreciable development took place and at 23–25°C. it was still retarded. The optimum development temperature was found to be 27–29°C, whilst 33–34°C. was actually detrimental.

A study of the length of life of the adult showed that survival was longest between 16–19°C. at which temperature it took 100 days to reach 50 per cent, mortality and 200 days a 100 per cent, mortality.

The fluctuation of the fly population in Israel is discussed in detail. It is pointed out that the prevalence of host fruits is one of the great factors responsible for these fluctuations. An analysis of the climatic conditions month by month and its influence upon the fly population is discussed. The curve depicting the fluctuations of the fly in the coastal plain has two depressions, one between December and January, and the other in July and August. In the Upper Jordan Valley, the summer depression was more clear-cut than in the maritime plain, and the spring population reached a much greater height than that in the autumn.

The fly appeared about two months later in the hills than in the plain, namely towards early June, and it disappeared also earlier, presenting a single peak in July and August.

Laboratory experiments were carried out to investigate the effect of carbon dioxide and breath odours on the flight activity of Stomoxys calcitrans (L.). The flies responded to an increase in carbon dioxide concentration by an increase in flight activity (measured as the number of flights or the number of take-offs). The extent of this response was dependent on the period of starvation before exposure and the level of the increase in the carbon dioxide concentration. Flies rapidly habituated or adapted to new levels of carbon dioxide. Expired human breath elicited a greater increase in flight activity than would be predicted from its carbon dioxide content, and it was shown that the increased activity was caused by breath odours acting synergistically with an increase in the carbon dioxide concentration.

Catches of Glossina morsitans morsitans Westw. and G. pallidipes Aust. attracted to an odour-baited trap in riverine woodland in Rhodesia declined by about three-quarters over a 50-day period in the hot dry season. Concurrent catches from refuges suggested that the decline in trap catches was due to a reduction in population densities rather than a decreasing responsiveness of tsetse to the trap. Of G. pallidipes marked and released 250, 1250 and 2250 m from the trap, the percentages recaptured in the trap after 5 days were about 20, 10 and 4, respectively, and after 40 days about 28, 15 and 13. The sustained responsiveness to the trap and efficiency with which marked flies were removed suggested that odour-baited traps at an economical spacing of roughly one per 10 km2 could produce effective control of G. pallidipes.

Age-specific life-table data were collected over a year for field and insectary populations of Phoracantha semipunctata (F.) on logs of Eucalyptus grandis in Malawi. Most mortality occurred in the larval stage, and the major mortality factor was intraspecific competition. Severe overcrowding led to a reduction in population density from one generation to the next. Overcrowding also led to a reduction in beetle size and to a shift in the sex ratio in favour of males. Elimination of potential breeding sites is recommended as an effective control measure for this pest.